Polyester polyols produced from dicarboxylic acid anhydrides, polyols and polyepoxides are known. In U.S. Pat. No. 4,403,093, such polyester polyols are produced by first reacting a 1,2-dicarboxylic acid anhydride with a polyol under conditions sufficient to form a half-ester with substantially no polyesterification product. The resultant half-ester is then reacted with a polyepoxide under conditions sufficient to form an ungelled polyester oligomer. The resultant polyester oligomers are described as being useful as resinous binders in high solid containing compositions. As described in that reference, the polyols used to form the half-ester are those which contain from 2 to 20 carbon atoms. Preferred are aliphatic polyols selected from the group of neopentyl glycol; 2,2,4-trimethylpentane-1,3-diol: 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxy- propionate; diethylene glycol; dipropylene glycol, 1,6-hexane diol: and trimethylol propane.